U.S. patent number 10,815,371 [Application Number 16/087,901] was granted by the patent office on 2020-10-27 for polyacetal resin composition and molded product thereof.
This patent grant is currently assigned to MITSUBISHI GAS CHEMICAL COMPANY, INC.. The grantee listed for this patent is MITSUBISHI GAS CHEMICAL COMPANY, INC.. Invention is credited to Masato Hirooka, Daisuke Sunaga.
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United States Patent |
10,815,371 |
Hirooka , et al. |
October 27, 2020 |
Polyacetal resin composition and molded product thereof
Abstract
A polyacetal resin composition and a molded product thereof are
provided which are excellent in thermal stability, little elution
of components of the resin composition upon brought into contact
with fuel, and good releasability from the mold at the time of
molding, and which is excellent in the points of thermal stability,
fuel oil resistance and mold releasability. Provided is a
polyacetal resin composition which includes (A) a polyacetal resin
and (B) a mold release agent, (B) the mold release agent is a
polyolefin-based wax and/or a polytetrafluoroethylene-based wax,
and a content of (B) the mold release agent in the polyacetal resin
composition is 0.01 part by mass or more and 1.0 part by mass or
less based on 100 parts by mass of (A) the polyacetal resin.
Inventors: |
Hirooka; Masato (Mie,
JP), Sunaga; Daisuke (Mie, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
MITSUBISHI GAS CHEMICAL COMPANY, INC. |
Tokyo |
N/A |
JP |
|
|
Assignee: |
MITSUBISHI GAS CHEMICAL COMPANY,
INC. (Tokyo, JP)
|
Family
ID: |
1000005141130 |
Appl.
No.: |
16/087,901 |
Filed: |
March 28, 2017 |
PCT
Filed: |
March 28, 2017 |
PCT No.: |
PCT/JP2017/012577 |
371(c)(1),(2),(4) Date: |
September 24, 2018 |
PCT
Pub. No.: |
WO2017/170508 |
PCT
Pub. Date: |
October 05, 2017 |
Prior Publication Data
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|
|
|
Document
Identifier |
Publication Date |
|
US 20190106565 A1 |
Apr 11, 2019 |
|
Foreign Application Priority Data
|
|
|
|
|
Mar 30, 2016 [JP] |
|
|
2016-067157 |
Oct 31, 2016 [JP] |
|
|
2016-212651 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08L
5/00 (20130101); C08K 5/01 (20130101); C08L
23/08 (20130101); C08L 59/00 (20130101); C08L
23/00 (20130101); C08L 59/02 (20130101); C08L
27/18 (20130101); B29C 33/62 (20130101); C08K
5/13 (20130101); C08K 5/12 (20130101); B29K
2059/00 (20130101); B29K 2995/0067 (20130101); B29K
2995/0069 (20130101) |
Current International
Class: |
C08L
59/02 (20060101); C08L 59/00 (20060101); C08L
23/00 (20060101); C08L 27/18 (20060101); C08L
23/08 (20060101); C08K 5/13 (20060101); C08K
5/12 (20060101); C08K 5/01 (20060101); B29C
33/62 (20060101); C08L 5/00 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
|
|
2000-7884 |
|
Jan 2000 |
|
JP |
|
2005-187728 |
|
Jul 2005 |
|
JP |
|
2008-19430 |
|
Jan 2008 |
|
JP |
|
2008-214490 |
|
Sep 2008 |
|
JP |
|
2009-132768 |
|
Jun 2009 |
|
JP |
|
2010-265438 |
|
Nov 2010 |
|
JP |
|
2011-32379 |
|
Feb 2011 |
|
JP |
|
2012-162589 |
|
Aug 2012 |
|
JP |
|
2012-233129 |
|
Nov 2012 |
|
JP |
|
2012-233131 |
|
Nov 2012 |
|
JP |
|
2013-112728 |
|
Jun 2013 |
|
JP |
|
2014-148626 |
|
Aug 2014 |
|
JP |
|
Other References
Kunihiko, electronic translation of JP 2012-233129, Nov. 2012.
cited by examiner .
Extended European Search Report in EP 17775045.2-1102, dated Nov.
19, 2020. cited by applicant .
International Search Report issued in International Application No.
PCT/JP2017/012577, dated Jun. 13, 2017. cited by applicant .
Written Opinion of the International Searching Authority in respect
to International Application No. PCT/JP2017/012577, dated Jun. 13,
2017. cited by applicant.
|
Primary Examiner: Mullis; Jeffrey C
Attorney, Agent or Firm: Greenblum & Bernstein,
P.L.C.
Claims
The invention claimed is:
1. A polyacetal resin composition which comprises (A) a polyacetal
resin, (B) a mold release agent, and (C) an antioxidant, wherein
(B) the mold release agent is a polyolefin-based wax and/or a
polytetrafluoroethylene-based wax, a content of (B) the mold
release agent in the polyacetal resin composition is 0.01 part by
mass or more and 1.0 part by mass or less based on 100 parts by
mass of (A) the polyacetal resin, and (C) the antioxidant is
selected from the group consisting of
pentaerythritol-tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]-
,
1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene,
and mixtures thereof.
2. The polyacetal resin composition according to claim 1, wherein
(B) the mold release agent is a polyethylene-based wax and/or a
polytetrafluoroethylene-based wax.
3. The polyacetal resin composition according to claim 2, wherein
(B) the mold release agent is a polyethylene-based wax, and a
viscosity average molecular weight of the polyethylene-based wax is
500 to 15,000.
4. The polyacetal resin composition according to claim 1, wherein a
content of (B) the mold release agent in the polyacetal resin
composition is 0.04 part by mass or more and 0.15 part by mass or
less based on 100 parts by mass of (A) the polyacetal resin.
5. The polyacetal resin composition according to claim 1, wherein
the (C) antioxidant is present in a content of 0.01 part by mass or
more and 3.0 parts by mass or less based on 100 parts by mass of
(A) the polyacetal resin.
6. The polyacetal resin composition according to claim 5, wherein
the content of (C) the antioxidant in the polyacetal resin
composition is 0.03 part by mass or more and 0.15 part by mass or
less based on 100 parts by mass of (A) the polyacetal resin.
7. A molded product obtained by molding the polyacetal resin
composition according to any one of claims 1 to 5 or 6.
8. The polyacetal resin composition according to any one of claims
1 to 5 or 6 which is used for a part brought into contact with
fuel.
9. The molded product according to claim 7, which is a part brought
into contact with fuel.
10. The molded product according to claim 9, wherein the fuel is
one kind or two or more kinds selected from the group consisting of
gasoline fuel, gasohol fuel, diesel fuel and biofuel.
Description
TECHNICAL FIELD
The present invention relates to a polyacetal resin composition and
a molded product thereof.
BACKGROUND ART
The polyacetal resin composition is excellent in a balance of
mechanical characteristics, thermal characteristics, electric
characteristics, slidability, moldability, etc., and has widely
been used for electric devices, automobile parts, precision
mechanical parts, etc., as structural materials and mechanical
parts, etc. For example, as automobile parts, it has been used for
large-sized parts such as a fuel conveying unit represented by a
fuel pump module or the like directly brought into contact with
fuel (fuel oil). In the polyacetal resin composition used for the
parts directly brought into contact the fuel, if elution of the
components of the resin composition brought into contact with the
fuel is large, it becomes a cause of lowering mechanical strength
of the parts.
From such a viewpoint, several polyacetal resin compositions used
for parts related to automobile use brought into contact with fuel
have been disclosed. For example, Patent document 1 discloses that
a molded product of a polyacetal resin composition containing a
specific hindered phenol-based antioxidant and a fatty acid calcium
salt with specific amounts, respectively, hardly deteriorates even
when it is immersed in a high temperature fuel for a long period of
time.
In addition, Patent document 2 discloses that a polyacetal resin
composition containing a specific hindered phenol-based antioxidant
and a fatty acid calcium salt each with a specific amount and a
molded product thereof have extremely excellent heat resistance,
solvent resistance and acid resistance, and can be applied to parts
brought into contact with fuel for automobiles, especially a diesel
fuel.
Further, Patent document 3 discloses that a molded product of a
polyacetal resin composition containing an antioxidant, a fatty
acid metal salt, a nitrogen-containing compound, a nucleating agent
and polyethylene glycol or polypropylene glycol each with a
specific amount has excellent durability even when it is directly
brought into contact with fuel for automobiles.
PRIOR ART DOCUMENTS
Patent Documents
Patent document 1: JP 2013-112728A
Patent document 2: JP 2011-32379A
Patent document 3: JP 2009-132768A
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
In the polyacetal resin composition used for the parts directly
brought into contact with fuel, when components of the eluted resin
composition are deposited on the surface of the part, these
materials become causes of poor appearance of the part and
malfunction of the apparatus using the part. In addition,
releasability from a mold when formed into a part directly brought
into contact with fuel is also important. That is, as a polyacetal
resin composition used for parts directly brought into contact with
fuel, it has been required from the market to obtain a polyacetal
resin composition which has not only good thermal stability but
also little elution of components of the resin composition upon
brought into contact with fuel, favorable in releasability from a
mold at the time of molding, and excellent in the points of thermal
stability, fuel oil resistance and mold releasability.
From such a viewpoint, the present inventors have investigated
about fuel oil resistance and releasability by using calcium
stearate which is a fatty acid calcium salt disclosed in the
above-mentioned Patent documents 1 to 3 or pentaerythritol
tetrastearate which is a fatty acid ester generally used as a mold
release agent, and as a result, it has been found that the
polyacetal resin compositions using these compounds are poor in
thermal stability or elution of components when it is brought into
contact with fuel is large, so that these were not satisfactory as
a polyacetal resin composition used for parts directly brought into
contact with fuel.
That is, an object of the present invention is to provide a
polyacetal resin composition and a molded product thereof which are
excellent in thermal stability, little elution of components of the
resin composition upon brought into contact with fuel, good
releasing property from a mold at the time of molding, thermal
stability, fuel oil resistance and mold releasability.
Means to Solve the Problems
The present inventors have intensively studied to solve the
above-mentioned problems, and as a result, they have found that a
polyacetal resin composition comprising a polyacetal resin and a
polyolefin-based wax and/or a polytetrafluoro-ethylene-based wax as
a mold release agent, and using a specific amount of the mold
release agent based on the polyacetal resin is excellent in thermal
stability, little elution of component of the resin composition
upon brought into contact with fuel and good releasability from a
mold at the time of molding, and which is excellent in the points
of thermal stability, fuel oil resistance and mold releasability,
whereby they have completed the present invention.
That is, the present invention is as follows.
[1] A polyacetal resin composition comprises (A) a polyacetal resin
and (B) a mold release agent, wherein (B) the mold release agent is
a polyolefin-based wax and/or a polytetrafluoroethylene-based wax,
and a content of (B) the mold release agent in the polyacetal resin
composition is 0.01 part by mass or more and 1.0 part by mass or
less based on 100 parts by mass of (A) the polyacetal resin. [2]
The polyacetal resin composition described in [1], wherein (B) the
mold release agent is a polyethylene-based wax and/or a
polytetrafluoroethylene-based wax. [3] The polyacetal resin
composition described in [1] or [2], wherein (B) the mold release
agent is a polyethylene-based wax, and a viscosity average
molecular weight of the polyethylene-based wax is 500 to 15,000.
[4] The polyacetal resin composition described in any one of [1] to
[3], wherein a content of (B) the mold release agent in the
polyacetal resin composition is 0.04 part by mass or more and 0.15
part by mass or less based on 100 parts by mass of (A) the
polyacetal resin. [5] The polyacetal resin composition described in
any one of [1] to [4], wherein the composition further comprises
(C) an antioxidant in an amount of 0.01 part by mass or more and
3.0 parts by mass or less based on 100 parts by mass of (A) the
polyacetal resin. [6] The polyacetal resin composition described in
[5], wherein (C) the antioxidant is one or more kinds selected from
the group consisting of
pentaerythritol-tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]-
,
1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene
and
3,3',3'',5,5',5''-hexa-tert-butyl-.alpha.,.alpha.',.alpha.''-(mesitylene--
2,4,6-triyl)tri-p-cresol. [7] The polyacetal resin composition
described in [5] or [6], wherein a content of (C) the antioxidant
in the polyacetal resin composition is 0.03 part by mass or more
and 0.15 part by mass or less based on 100 parts by mass of (A) the
polyacetal resin. [8] A molded product obtained by molding the
polyacetal resin composition described in any one of [1] to [7].
[9] The polyacetal resin composition described in [1] to [7], which
is used for a part brought into contact with fuel. [10] The molded
product described in [8], which is a part brought into contact with
fuel. [11] The molded product described in [10], wherein the fuel
is one kind or two or more kinds selected from the group consisting
of gasoline fuel, gasohol fuel, diesel fuel and biofuel.
Effects of the Invention
According to the present invention, it is possible to provide a
polyacetal resin composition and a molded product thereof which are
excellent in thermal stability, little elution of components of the
resin composition upon brought into contact with fuel and good
releasability from a mold at the time of molding, and which is
excellent in the points of thermal stability, fuel oil resistance
and mold releasability.
BRIEF DESCRIPTION OF THE DRAWING
The FIGURE shows a schematic drawing of an apparatus used for
evaluation of fuel oil resistance in Examples and Comparative
examples.
EMBODIMENTS TO CARRY OUT THE INVENTION
In the following, the present invention is explained in detail. The
polyacetal resin composition of the present invention comprises (A)
a polyacetal resin and (B) a mold release agent, wherein (B) the
mold release agent is a polyolefin-based wax and/or a
polytetrafluoroethylene-based wax, and a content of (B) the mold
release agent in the polyacetal resin composition is 0.01 part by
mass or more and 1.0 part by mass or less based on 100 parts by
mass of (A) the polyacetal resin. Such a polyacetal resin
composition has characteristics that it is excellent in thermal
stability, little elution of components of the resin composition
upon brought into contact with fuel, and good releasability from a
mold at the time of molding, and which is excellent in the points
of thermal stability, fuel oil resistance and mold releasability.
The reason thereof is not particularly limited, and it can be
thought that when the polyacetal resin composition contains a
specific amount(s) of the polyolefin-based wax and/or
polytetrafluoro-ethylene-based wax, the polyacetal resin
composition is excellent in thermal stability and releasability of
the polyacetal resin composition from a mold is good, and the
polyolefin-based wax and/or the polytetrafluoroethylene-based wax
has low solubility in fuel or low reactivity with fuel as mentioned
below.
The polyacetal resin composition of the present invention can be
suitably used for parts that brought into contact with fuel. Here,
the fuel is not particularly limited, and may be referred to, for
example, an aliphatic and/or aromatic hydrocarbon compound which
may have a hetero atom(s) in a solid, liquid or gas (vapor) state
including gasoline fuel, gasohol fuel, diesel fuel, biofuel, and a
solid fuel such as wax, etc.
In the following, the components constituting the polyacetal resin
composition of the present invention are explained.
<(A) Polyacetal Resin>
The polyacetal resin composition of the present invention contains
(A) a polyacetal resin. The (A) polyacetal resin is a polymer
having an acetal bond: --O--CRH-- (here, R represents a hydrogen
atom or an organic group) as a recurring unit, and generally
comprises an oxymethylene group (--OCH.sub.2--) where R is a
hydrogen atom as a main constitutional unit. The polyacetal resin
to be used in the present invention contains a copolymer (block
copolymer) or a terpolymer which contains one or more kinds of a
recurring constitutional unit other than the above-mentioned
oxymethylene group, and further includes not only a linear
structure but also a branched or crosslinked structure formed by
using a glycidyl ether compound, an epoxy compound, an allyl ether
compound, etc., as a comonomer and/or a termonomer. The
constitutional unit other than the above-mentioned oxymethylene
group may be mentioned, for example, an oxyalkylene group which may
be branched having 2 or more and 10 or less carbon atoms such as an
oxyethylene group (--OCH.sub.2CH.sub.2-- or --OCH(CH.sub.3)--), an
oxypropylene group (--OCH.sub.2CH.sub.2CH.sub.2--,
--OCH(CH.sub.3)CH.sub.2-- or --OCH.sub.2CH(CH.sub.3)--), an
oxybutylene group (--OCH.sub.2CH.sub.2CH.sub.2CH.sub.2--,
--OCH(CH.sub.3)CH.sub.2CH.sub.2--,
--OCH.sub.2CH(CH.sub.3)CH.sub.2--,
--OCH.sub.2CH.sub.2CH(CH.sub.3)--, --OCH(C.sub.2H.sub.5)CH.sub.2--
or --OCH.sub.2CH(C.sub.2H.sub.5)--), etc., among these, preferably
an oxyalkylene group which may be branched and having 2 or more and
4 or less carbon atoms, and particularly preferably an oxyethylene
group (--OCH.sub.2CH.sub.2--). In addition, the content of the
constitutional unit (an oxyalkylene group) other than the
oxymethylene group in (A) the polyacetal resin is preferably 0.1%
by mass or more and 20% by mass or less, more preferably 0.5% by
mass or more and 15% by mass or less, and further preferably 0.5%
by mass or more and 6.0% by mass or less.
The method for producing (A) the polyacetal resin is not
particularly limited, and it may be produced by any conventionally
known method. For example, as a method for producing (A) the
polyacetal resin having an oxymethylene group and an oxyalkylene
group having 2 to 4 carbon atoms as a constitutional unit, it can
be produced by copolymerizing a cyclic acetal of an oxymethylene
group such as a trimer (trioxane) or a tetramer (tetraoxane) of
formaldehyde, etc., and a cyclic acetal containing an oxyalkylene
group having 2 or more and 5 or less carbon atoms such as ethylene
oxide, 1,3-dioxolane, 1,3,6-trioxocane, 1,3-dioxepane, etc. Among
these, (A) the polyacetal resin that can be used in the present
invention is preferably a copolymer of a cyclic acetal such as
trioxane, tetraoxane, etc., and ethylene oxide or 1,3-dioxolane,
particularly preferably a copolymer of trioxane and
1,3-dioxolane.
The (A) polyacetal resin can be obtained, for example, by a method
of bulk polymerization of a cyclic acetal of an oxymethylene group
and a cyclic acetal containing an oxyalkylene group having 2 or
more and 5 or less carbon atoms which is a comonomer using a
polymerization catalyst. For deactivation treatment of the
polymerization catalyst and the polymerization growth terminal, a
reaction terminator may be used, if necessary. In addition, a
molecular weight controller may be used as required for controlling
the molecular weight of (A) the polyacetal resin. The kind and
amount of the polymerization catalyst, the reaction terminator and
the molecular weight controller that can be used for producing (A)
the polyacetal resin of the present invention are not particularly
limited as long as they do not inhibit the effect of the present
invention, and any conventionally known optional polymerization
catalyst, reaction terminator and molecular weight controller may
be appropriately used.
The polymerization catalyst is not particularly limited and it may
be mentioned, for example, a Lewis acid such as boron trifluoride,
tin tetrachloride, titanium tetrachloride, phosphorus
pentachloride, phosphorus pentafluoride, arsenic pentafluoride and
antimony pentafluoride, etc., and a complex compound or a salt
compound of these Lewis acids. In addition, there may be also
mentioned a protonic acid such as trifluoromethanesulfonic acid and
perchloric acid, etc.; an ester of a protonic acid such as an ester
of perchloric acid and a lower aliphatic alcohol, etc.; and an
anhydride of a protonic acid such as a mixed anhydride of
perchloric acid and a lower aliphatic carboxylic acid, etc. Other
than the above, there may be mentioned triethyloxonium
hexafluorophosphate, triphenylmethyl hexafluoroarsenate, acetyl
hexafluoroborate, a heteropoly acid or an acid salt thereof, an
isopolyacid or an acid salt thereof, a perfluoroalkylsulfonic acid
or an acid salt thereof. Among these, a compound containing boron
trifluoride is preferable, and boron trifluoride diethyl etherate
and boron trifluoride dibutyl etherate, which are coordination
complexes with an ether, are particularly preferable.
The amount of the polymerization catalyst to be used is not
particularly limited, and is usually 1.0.times.10.sup.-8 to
2.0.times.10.sup.-3 mol, preferably 5.0.times.10.sup.-8 to
8.0.times.10.sup.-4 mol, particularly preferably in the range of
5.0.times.10.sup.-8 to 1.0.times.10.sup.-4 mol based on 1 mol of
the total monomers in sum of trioxane and comonomer(s).
The reaction terminator is not particularly limited and, for
example, there may be mentioned a trivalent organic phosphorus
compound, an amine compound or a hydroxide of an alkali metal or
alkaline earth metal. These reaction terminators can be used singly
or in combination of two or more kinds. Among these, a trivalent
organic phosphorus compound, a tertiary amine and a hindered amine
are preferable.
An amount of the reaction terminator to be used is not particularly
limited as long as it is an amount sufficient to inactivate the
polymerization catalyst, and it is usually in the range of
1.0.times.10.sup.-1 to 1.0.times.10.sup.1 as a molar ratio based on
the polymerization catalyst.
The molecular weight controller is not particularly limited and may
be mentioned, for example, methylal, methoxymethylal,
dimethoxymethylal, trimethoxymethylal, oxymethylene di-n-butyl
ether, etc. Among these, methylal is preferable. An amount of these
molecular weight controllers to be used is appropriately determined
according to the targeted molecular weight. In general, an addition
amount is adjusted in the range of 0 to 0.1% by mass based on the
total monomers.
<(B) Mold Release Agent>
It is essential that the polyacetal resin composition of the
present invention contains (B) a mold release agent, and a
polyolefin-based wax and/or a polytetra-fluoroethylene-based wax is
used as (B) the mold release agent. This is because the polyacetal
resin composition contains a polyolefin-based wax and/or a
polytetra-fluoroethylene-based wax as (B) the mold release agent,
so that elution of components of the resin composition upon brought
into contact with fuel is little, releasability from a mold at the
time of molding is good, and the balance between fuel oil
resistance and mold releasability is excellent. In addition, the
polyacetal resin composition to which the polyolefin-based wax or
the polytetrafluoroethylene-based wax is added has a characteristic
that it is excellent in thermal stability than that of a resin
composition to which a fatty acid calcium salt (for example,
calcium stearate) or a fatty acid ester (for example,
pentaerythritol tetrastearate) to be generally used as a mold
release agent is added. The polyolefin-based wax or the
polytetrafluoroethylene-based wax may be used one kind alone, or
two or more kinds in combination. Among these, a polyethylene-based
wax and/or a polytetrafluoroethylene-based wax, which will be
mentioned later, is preferable as (B) the mold release agent.
The polyolefin-based wax is not particularly limited as long as it
is chemically synthesized low molecular weight polymer (synthetic
wax) having a skeleton derived from an olefin and may be mentioned,
for example, a polyethylene-based wax, a polypropylene-based wax,
an ethylene-acrylic acid copolymer wax, an ethylene-vinyl acetate
copolymer wax, etc. Also, it may be a material to which a polar
group is introduced by subjecting to oxidation modification or acid
modification of these waxes. The polyolefin-based wax may be used
one kind alone, or two or more kinds in which a kind or viscosity
is different from each other in combination.
A molecular weight of the polyolefin-based wax is not particularly
limited, and it is preferably 500 to 30,000, more preferably 500 to
15,000, further preferably 1,000 to 10,000, and particularly
preferably 2,000 to 8,000 in terms of a viscosity average molecular
weight. If the viscosity average molecular weight of the
polyolefin-based wax is 500 or more, elution of the mold release
agent when it is brought into contact with the fuel tends to be
suppressed. On the other hand, if the viscosity average molecular
weight is 30,000 or less, releasability at the time of molding
tends to be favorable by adding a small amount of the mold release
agent.
As (B) the mold release agent, among the above-mentioned
polyolefin-based waxes, it is preferable to be the
polyethylene-based wax and/or the polypropylene-based wax, and
particularly preferably the polyethylene-based wax.
The polyethylene-based wax is not particularly limited as long as
it is a low molecular weight polymer having a skeleton derived from
ethylene and may be mentioned, for example, a low molecular weight
polyethylene polymer (hereinafter simply referred to as a low
molecular weight polyethylene) or a low molecular weight
polyethylene copolymer, and an oxidation-modified polyethylene wax
or an acid-modified polyethylene wax to which a polar group is
introduced by subjecting to oxidation modification or acid
modification thereof. These low molecular weight polyethylene, low
molecular weight polyethylene copolymer, oxidation-modified
polyethylene wax and acid-modified polyethylene wax may be used one
kind alone or two or more kinds in combination.
The low molecular weight polyethylene is a low molecular weight
polymer obtained by polymerizing ethylene, and its structure may be
linear (high density polyethylene) or branched (low density
polyethylene).
The low molecular weight polyethylene copolymer is a low molecular
weight copolymer obtained by polymerizing ethylene and an
.alpha.-olefin, and its structure may be linear (high density
polyethylene) or branched (low density polyethylene). The low
molecular weight polyethylene copolymer is preferably a low
molecular weight polyethylene copolymer in which the .alpha.-olefin
is propylene.
A composition ratio of ethylene and an .alpha.-olefin in the low
molecular weight polyethylene copolymer is not particularly
limited, and it is preferable that the ethylene content is 50 mol %
or more and less than 100 mol % and the .alpha.-olefin content is
more than 0 mol % and 50 mol % or less based on the total molar
content of ethylene and .alpha.-olefin in the low molecular weight
polyethylene copolymer. When the .alpha.-olefin is propylene, it is
preferable that the ethylene content is 50 mol % or more and less
than 100 mol % and the propylene content is more than 0 mol % and
50 mol % or less based on the total molar content of ethylene and
propylene in the low molecular weight polyethylene copolymer.
The method for producing the low molecular weight polyethylene or
the low molecular weight polyethylene copolymer is not particularly
limited, and it may be produced by, for example, a method of
directly polymerizing ethylene or ethylene and an .alpha.-olefin
with a Ziegler catalyst, etc., a method of obtaining as a
by-product at the time of producing a high molecular weight
polyethylene or a copolymer, a method of thermally decomposing a
high molecular weight polyethylene or a copolymer, or the like.
The oxidation-modified polyethylene wax is not particularly limited
as long as it is a product obtained by treating the above-mentioned
low molecular weight polyethylene polymer or low molecular weight
polyethylene copolymer with a peroxide, oxygen or the like to
introduce a polar group such as a carboxyl group, a hydroxyl group,
etc.
The acid-modified polyethylene wax is not particularly limited as
long as it is a material to which a polar group such as a carboxyl
group, a sulfonic acid group, etc., is introduced to the
above-mentioned low molecular weight polyethylene polymer or low
molecular weight polyethylene copolymer by treating with inorganic
acid, an organic acid, an unsaturated carboxylic acid, etc., if
necessary, in the presence of a peroxide or oxygen.
A viscosity average molecular weight of the polyethylene-based wax
is not particularly limited, and preferably 500 to 15,000, more
preferably 1,000 to 10,000, and particularly preferably 2,000 to
8,000. If the viscosity average molecular weight of the
polyethylene-based wax is 500 or more, elution of the mold release
agent when it is brought into contact with the fuel tends to be
suppressed. On the other hand, if the viscosity average molecular
weight is 15,000 or less, releasability at the time of molding
tends to be favorable by adding a small amount of the mold release
agent.
The above-mentioned polyethylene-based wax may be used a single
kind alone, or two or more kinds in which a kind or viscosity is
different from each other in combination.
The above-mentioned polyethylene-based wax may be a commercially
available product and a material that is commercially sold under
the name of, for example, general polymerization type high density
type polyethylene wax, general polymerization type low density type
polyethylene wax, oxidation type polyethylene wax (small acid
value), oxidation type polyethylene wax (high acid value),
acid-modified type polyethylene wax, specific monomer-modified type
polyethylene wax, or low density polyethylene general type
polyethylene wax, etc., may be used. For example, as the oxidation
type polyethylene wax, Hi-WAX 220MP available from Mitsui
Chemicals, Inc., can be used. Also, as the high density type
polyethylene wax, Hi-WAX 800P available from Mitsui Chemicals,
Inc., can be used.
The polytetrafluoroethylene-based wax is not particularly limited
as long as it is a polymer having a tetrafluoroethylene skeleton
and may be mentioned, for example, polytetrafluoroethylene (PTFE),
and a copolymer of a tetrafluoroethylene and other monomer(s).
Among these, polytetrafluoroethylene is preferable, and low
molecular weight polytetrafluoroethylene is particularly
preferable.
The low molecular weight polytetrafluoroethylene is not
particularly limited and may be mentioned, for example, powder
state polytetrafluoroethylene (PTFE powder), fibrous
polytetrafluoroethylene (PTFE fiber) and aqueous dispersion liquid
state polytetrafluoroethylene (PTFE dispersion), and PTFE powder is
particularly preferable from the viewpoint of dispersibility.
As the low molecular weight polytetrafluoroethylene, commercially
available products may be used and may be mentioned, for example,
Lubron L5 (Registered Trademark) available from Daikin Industries,
Ltd., as the PTFE powder.
A content of (B) the mold release agent in the polyacetal resin
composition of the present invention is 0.01 part by mass or more
and 1.0 part by mass or less based on 100 parts by mass of (A) the
polyacetal resin. If the content of (B) the mold release agent in
the polyacetal resin composition is 0.01 part by mass or more,
releasability of the molded product from a mold tends to be
favorable. On the other hand, if the content thereof is 1.0 part by
mass or less, thermal stability and fuel oil resistance tend to be
excellent.
The content of (B) the mold release agent in the polyacetal resin
composition is preferably 0.02 part by mass or more and 0.7 part by
mass or less, more preferably 0.03 part by mass or more and 0.2
part by mass or less, further preferably 0.04 part by mass or more
and 0.15 part by mass or less, and particularly preferably 0.08
part by mass or more and 0.12 part by mass or less based on 100
parts by mass of (A) the polyacetal resin. If the content of (B)
the mold release agent is 0.03 part by mass or more and 0.2 part by
mass or less, the resin composition and the molded product are
excellent in the points of thermal stability, fuel oil resistance
and mold releasability, if it is 0.04 part by mass or more and 0.15
part by mass or less, these are more excellent in the points of
thermal stability, fuel oil resistance and mold releasability, and
if it is 0.08 part by mass or more and 0.12 part by mass or less,
these are particularly excellent in the points of thermal
stability, fuel oil resistance and mold releasability.
<(C) Antioxidant>
The polyacetal resin composition of the present invention
preferably further comprises (C) an antioxidant. When the
polyacetal resin composition contains (C) the antioxidant, heat
resistance of the resin composition is improved, so that the
thermal stability at the time of molding process tends to be
excellent, and as a result, a molded product favorable in
mechanical strength and fuel oil resistance tends to be
obtained.
A kind of (C) the antioxidant is not particularly limited and may
be mentioned, for example,
ethylenebis(oxyethylene)bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate]
(for example, BASF, IRGANOX (Registered Trademark) 245),
N,N'-hexan-1,6-diylbis[3-(3,5-di-tert-butyl-4-hydroxyphenylpropionamide]
(for example, BASF, IRGANOX (Registered Trademark) 1098),
pentaerythritoltetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]
(for example, BASF, IRGANOX (Registered Trademark) 1010),
1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene
(for example, Rianlon, THANOX (Registered Trademark) 330),
3,3',3'',5,5',5''-hexa-tert-butyl-.alpha.,.alpha.',.alpha.''-(mesitylene--
2,4,6-triyl)tri-p-cresol (for example, BASF, IRGANOX (Registered
Trademark) 1330) and
1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazin-2,4,6(1H,3H,5-
H)-trion (for example, BASF, IRGANOX (Registered Trademark)
3114).
Among these, it is more preferable that (C) the antioxidant is one
or more kinds selected from the group consisting of
pentaerythritol-tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]
(for example, BASF, IRGANOX (Registered Trademark) 1010),
1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene
(for example, Rianlon, THANOX (Registered Trademark) 330), and
3,3',3'',5,5',5''-hexa-tert-butyl-.alpha.,.alpha.',.alpha.''-(mesitylene--
2,4,6-triyl)tri-p-cresol (for example, BASF, IRGANOX (Registered
Trademark) 1330), since elution of (C) the antioxidant from the
resin composition and the molded product difficultly occurs and
fuel oil resistance is excellent while maintaining thermal
stability of the resin composition and the molded product by (C)
the antioxidant. Further, it is particularly preferable that (C)
the antioxidant is
1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene
(for example, Rianlon, THANOX (Registered Trademark) 330) and/or
3,3',3'',5,5',5''-hexa-tert-butyl-.alpha.,.alpha.',.alpha.''-(mesitylene--
2,4,6-triyl)tri-p-cresol (for example, BASF, IRGANOX (Registered
Trademark) 1330) since the resin composition and the molded product
are particularly excellent in thermal stability and fuel oil
resistance.
A content of (C) the antioxidant in the polyacetal resin
composition is not particularly limited, and is preferably 0.01
part by mass or more and 3.0 parts by mass or less based on 100
parts by mass of (A) the polyacetal resin. If the content of (C)
the antioxidant in the resin composition is 0.01 part by mass or
more, heat resistance of the resin composition and the molded
product tends to be improved. On the other hand, if the content is
3.0 parts by mass or less, elution of (C) the antioxidant from the
resin composition and the molded product difficultly occurs, fuel
oil resistance is excellent, and mold releasability tends to be
excellent. In addition, the content of (C) the antioxidant is more
preferably 0.01 part by mass or more and 0.5 part by mass or less,
further preferably 0.02 part by mass or more and 0.2 part by mass
or less, and particularly preferably 0.03 part by mass or more and
0.15 part by mass or less. When the content of (C) the antioxidant
is 0.02 part by mass or more and 0.2 part by mass or less, the
resin composition and the molded product are excellent in the
points of thermal stability, fuel oil resistance and mold
releasability, and when it is 0.03 part by mass or more and 0.15
part by mass or less, these are particularly excellent in the
points of thermal stability, fuel oil resistance and mold
releasability.
In a preferred embodiment of the present invention, by using a
polyolefin-based wax and/or a polytetrafluoroethylene-based wax as
(B) a mold release agent in combination with (C) an antioxidant,
fuel oil resistance is excellent, as well as mold releasability and
thermal stability are also excellent.
<Other Optional Ingredients that May be Added>
Further, when practicing the present invention, a
nitrogen-containing compound other than (C) the antioxidant, and a
metal-containing compound represented by the group consisting of a
hydroxide, a carbonate, an inorganic acid salt and an alkoxide of
an alkali metal or an alkaline earth metal may further be added
within the range which does not impair the objects of the present
invention.
The nitrogen-containing compound is not particularly limited and
may be mentioned, for example, an amino-substituted triazine
compound, a polyamide resin and a hindered amine compound.
An amount of the nitrogen-containing compound to be added is not
particularly limited, and is preferably 0.01 to 5.0 parts by mass,
more preferably 0.01 to 3.0 parts by mass, and particularly
preferably 0.02 to 2.0 parts by mass based on 100 parts by mass of
(A) the polyacetal resin. If the amount of the nitrogen-containing
compound to be added is 0.01 part by mass or more, thermal
stability of the polyacetal resin composition is improved, while if
the amount thereof to be added is 5.0 parts by mass or less,
thermal stability of the polyacetal resin composition can be
improved without accompanying marked lowering in tensile elongation
and impact resistance.
The amino-substituted triazine compound is not particularly limited
and may be mentioned, for example, methylol melamine such as
guanamine, melamine, N-butylmelamine, N-phenylmelamine,
N,N-diphenylmelamine, N,N-diallylmelamine,
N,N',N''-triphenylmelamine, N,N',N''-trimethylol melamine, etc., an
alkylated melamine such as hexamethoxymethylmelamine, etc.,
benzoguanamine, 2,4-diamino-6-methyl-sym-triazine,
2,4-diamino-6-butyl-sym-triazine,
2,4-diamino-6-benzyloxy-sym-triazine,
2,4-diamino-6-butoxy-sym-triazine,
2,4-diamino-6-cyclohexyl-sym-triazine,
2,4-diamino-6-chloro-sym-triazine,
2,4-diamino-6-mercapto-sym-triazine, ammeline
(N,N,N',N'-tetracyanoethylbenzo-guanamine), a water-soluble
melamine-formaldehyde resin, etc. Among these, melamine, methylol
melamine, alkylated melamine, benzoguanamine, and a water-soluble
melamine-formaldehyde resin are preferable. The above-mentioned
amino-substituted triazine compound may be used alone, or two or
more kinds thereof may be used in combination. These
amino-substituted triazine compounds are used as a heat-resistant
stabilizer.
The polyamide resin is not particularly limited as long as it is a
resin having two or more amide bonds in the molecule and may be
mentioned, for example, Nylon 6, Nylon 6,6, Nylon 6,10, a ternary
copolymer thereof, a polymerized fatty acid-based polyamide resin
and a polyamide elastomer, etc. Among these, a polymerized fatty
acid-based polyamide resin or a polyamide elastomer are
particularly preferable. These polyamide resins may be used one
kind alone, or two or more kinds thereof in combination.
Here, the polymerized fatty acid-based polyamide resin refers to a
polyamide resin composed of a polycondensate of a polymerized fatty
acid and a diamine.
The polymerized fatty acid is a polymer of an unsaturated fatty
acid, or a material obtained by hydrogenating the polymer, and the
polymerized fatty acid may be mentioned, for example, a dimer
(dimer acid) of a monobasic fatty acid having 10 to 24 carbon atoms
and having one or more double bond or triple bond or hydrogenated
product thereof. The dimer acid may be mentioned, for example,
dimers of such as oleic acid, linoleic acid and erucic acid,
etc.
Examples of the diamine may be mentioned hexamethylenediamine,
heptamethylenediamine, octamethylenediamine, decamethylenediamine
and m-xylylenediamine, etc.
The polyamide elastomer refers to a polyamide resin having a hard
segment and a soft segment, the hard segment comprising polyamide,
and the soft segment comprising a polymer other than the polyamide.
The polyamide constituting the hard segment may be mentioned, for
example, Nylon 6, Nylon 6,6, Nylon 6,10, a ternary copolymer
thereof, a polymerized fatty acid-based polyamide resin, etc. The
polymer other than the polyamide may be mentioned, for example, an
aliphatic polyester and an aliphatic polyether. The aliphatic
polyester may be mentioned, for example,
poly(.epsilon.-caprolactone), polyethylene adipate, polybutylene
adipate and polybutylene succinate, etc. The aliphatic polyether
may be mentioned, for example, polyoxyalkylene glycol such as
polyethylene oxide, polypropylene oxide, etc.
The hindered amine compound is not particularly limited and may be
mentioned, for example,
N,N',N'',N'''-tetrakis-(4,6-bis-(butyl-(N-methyl-2,2,6,6-tetramethylpiper-
idin-4-yl)amino)-triazin-2-yl)-4,7-diazadecane-1,10-diamine, a
polycondensate of dibutylamine 1,3,5-triazine
N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl-1,6-hexamethylenediamine
and N-(2,2,6,6-tetramethyl-4-piperidyl)butylamine (BASF, Chimassorb
(Registered Trademark) 2020 FDL),
poly[{6-(1,1,3,3-tetramethyl-butyl)amino-1,3,5-triazin-2,4-diyl}{(2,2,6,6-
-tetramethyl-4-piperidyl}imino)hexa-methylene{(2,2,6,6-tetramethyl-4-piper-
idyl)imino}], a polycondensate of dimethyl succinate and
4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol (BASF, Tinuvin
(Registered Trademark) 622 SF),
bis(1,2,2,6,6-pentamethyl-4-piperidyl)[[3,5-bis(1,1-dimethylethyl)-4-hydr-
oxyphenyl]methyl]butylmalonate,
bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate,
bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, and
1-[2-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy]ethyl]-4-[3-(3,5-di--
t-butyl-4-hydroxyphenyl)propionyloxy]-2,2,6,6-tetramethylpiperidine.
Among these, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate,
bis(1,2,2,6,6-pentamethyl-4-piperidyl)-sebacate and a
polycondensate of dimethyl succinate and
4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol (BASF, Tinuvin
(Registered Trademark) 622 SF) are preferable. The above-mentioned
hindered amine compound may be used one kind alone or two or more
kinds in combination. These hindered amine compounds are used as a
light stabilizer and an antioxidant.
As the inorganic acid salt in the metal-containing compound
represented by the group consisting of a hydroxide, a carbonate, an
inorganic acid salt and an alkoxide of an alkali metal or an
alkaline earth metal, there may be mentioned a phosphate, a
silicate, a borate, etc., and the alkoxide may be mentioned
methoxide, ethoxide, etc. Among these, preferred are a hydroxide, a
carbonate, an inorganic acid salt or an alkoxide of an alkaline
earth metal, and more preferred are calcium hydroxide, magnesium
hydroxide, calcium carbonate, or magnesium carbonate.
An amount of the metal-containing compound represented by the group
consisting of a hydroxide, a carbonate, an inorganic acid salt and
an alkoxide of an alkali metal or an alkaline earth metal to be
added is not particularly limited, and is preferably 0.001 to 5.0
parts by mass, particularly preferably 0.01 to 3.0 parts by mass
based on 100 parts by mass of (A) the polyacetal resin.
Also, when the present invention is practiced, various kinds of
light stabilizers, ultraviolet absorbers, lubricants other than (B)
the mold release agent, nucleating agents, fillers, pigments,
surfactants, antistatic s, etc., may be further added within the
range which do not impair the object of the present invention.
<Method for Producing Polyacetal Resin Composition>
The method for producing the polyacetal resin composition of the
present invention is not particularly limited as long as it is a
method in which the above-mentioned (A) polyacetal resin and the
polyolefin-based wax and/or the polytetrafluoroethylene-based wax
as (B) the mold release agent are mixed and then subjected to
melting and kneading, and a conventionally known method for
producing a polyacetal resin composition can be used. For example,
it can be produced by mixing the above-mentioned (A) polyacetal
resin, the polyolefin-based wax and/or the
polytetrafluoroethylene-based wax, and depending on necessity, (C)
the antioxidant and the above-mentioned other optional component(s)
which may be added with an optional order, and subjected to melting
and kneading them.
The conditions of a temperature and a pressure for melting and
kneading may be appropriately selected according to a
conventionally known method for producing a polyacetal resin
composition, and are not particularly limited. For example, the
temperature for melting and kneading is preferably the melting
temperature of (A) the polyacetal resin or higher and 270.degree.
C. or lower, and particularly preferably 190.degree. C. or higher
and 250.degree. C. or lower. Also, the pressure at the time of
melting and kneading is preferably 6.7 kPa or more and 66.7 kPa or
less, and particularly preferably 13.3 kPa or more and 40.0 kPa or
less in the absolute pressure. A time (residence time in the
apparatus used for melting and kneading) for carrying out the
melting and kneading is not particularly limited, and is preferably
1 to 60 minutes, particularly preferably 1 to 40 minutes.
An apparatus used for melting and kneading is also not particularly
limited, and a melt-kneading apparatus such as a single-screw or
twin-screw extruder, etc., conventionally used for producing this
type of resin composition can be used. There is also no particular
limitation on the method of melting and kneading and a polyacetal
resin composition (pellets) can be obtained, for example, by
continuously extrusion molding with devolatilization under the
above-mentioned temperature and pressure using the above-mentioned
single-screw or twin-screw extruder.
Specifically, for example, a polyolefin-based wax and/or a
polytetrafluoro-ethylene-based wax is/are added to (A) the
polyacetal resin, and if desired, (C) the antioxidant and/or the
above-mentioned other optional component(s) which may be added
is/are further added, followed by mixing with a tumbler type
blender, etc. Then, the obtained mixture is melted and kneaded by a
single-screw or twin-screw extruder, extruded in a strand form, and
pelletized, whereby a polyacetal resin composition having a desired
composition can be obtained.
As another method, a polyolefin-based wax and/or a
polytetrafluoroethylene-based wax is/are added to (A) the
polyacetal resin and mixed, and then, melted and kneaded, and
pelletized. The (C) antioxidant and/or the above-mentioned other
optional component(s) which may be added, etc., is/are further
added to the pellets, if desired, and then the mixture is mixed,
melted and kneaded again and pelletized to obtain a polyacetal
resin composition having a desired composition. In addition, the
resin composition melted and kneaded by the extruder can be
directly made into injection molded products, blow molded products,
extrusion molded products or the like without passing through the
pellets.
<Molded Product of Polyacetal Resin Composition and Use
Thereof>
The polyacetal resin composition of the present invention can be
molded into various forms according to a known molding process of a
polyacetal resin. The molded product comprising the polyacetal
resin composition of the present invention may be mentioned various
shapes such as pellets, round bars, thick plates, sheets, tubes,
cylindrical or rectangular containers, and the invention is not
limited thereto.
The polyacetal resin composition of the present invention and the
molded product thereof can be used as various parts machinery,
electricity, automobiles, building materials and others which are
conventionally known for use of the polyacetal resin composition,
and in particular, they are suitable for use as a part of a fuel
tank cap, etc., which is directly brought into contact with a
solid, a liquid, a gas (particularly steam) of a fuel to be
mentioned later.
The fuel in the present invention is, as mentioned above, not
particularly limited, and is a solid, a liquid or a gas
(particularly steam) state fuel containing an aliphatic and/or
aromatic hydrocarbon compound which may have a hetero atom(s), and
may be mentioned, for example, gasoline fuel, gasohol fuel, diesel
fuel and biofuel. These fuels may be one kind or may be a mixture
of two or more kinds. The gasoline fuel is not particularly limited
as long as it is a petroleum product that is generally used as fuel
for an automobile, and does not indicate a special fuel. The
gasohol fuel is not particularly limited as long as it is a mixture
of gasoline and an alcohol such as methanol, ethanol, etc. The
diesel fuel is not particularly limited as long as it is a
petroleum product used as fuel for a diesel engine and may be
mentioned, for example, light oil. The biofuel is not particularly
limited as long as it is fuel produced from reproducible organic
resources (biomass) derived from organisms as a raw material.
EXAMPLES
In the following, the present invention will be specifically
explained with regard to the embodiments and the effects thereof by
showing Examples and Comparative examples, but the present
invention is not limited by these examples at all.
The polyacetal resin compositions in Examples and Comparative
examples were prepared as follows.
<Production of (A) Polyacetal Resin>
To a biaxial continuous polymerization apparatus having a
self-cleaning type paddle having a jacket the temperature of which
was set at 65.degree. C. were added continuously 100 parts by mass
of trioxane, 4 parts by mass of 1,3-dioxolane, boron trifluoride
diethyl etherate as a catalyst with such an amount that became 0.05
mmol based on 1 mol of whole monomer (trioxane and 1,3-dioxolane)
as a benzene solution, and methylal as a molecular weight
controller with such an amount that became 500 ppm based on whole
monomer as a benzene solution, and the polymerization reaction was
continuously carried out so that the residence time of the raw
materials and the polymerization reaction product in the continuous
polymerization apparatus became 20 minutes.
To the obtained polymerization reaction product was added
triphenylphosphine with such an amount that became 2 mol based on 1
mol of the used boron trifluoride diethyl etherate as a benzene
solution. After inactivating the catalyst, it was pulverized to
obtain (A) a polyacetal resin.
<Production of Polyacetal Resin Composition>
The (A) polyacetal resin, (B) the mold release agent and (C) the
antioxidant were mixed with the formulation amount (unit: part(s)
by mass) shown in Table 1 to Table 3, and melted under heating in
the temperature range of 210 to 230.degree. C. in a twin-screw
extruder with a bore diameter of 30 mm and devolatilized under
reduced pressure of 21.3 kPa to prepare pellets of the polyacetal
resin compositions of Examples 1 to 16 and Comparative examples 1
to 4.
The meaning of the symbols described in Examples and Comparative
examples in Table 1 to Table 3 are shown as follows.
<B: Mold Release Agent>
B-1: Polyethylene-based wax (Hi-WAX 220MP, available from Mitsui
Chemicals, Inc., molecular weight 2,000)
B-2: Polyethylene-based wax (Hi-WAX 800P, available from Mitsui
Chemicals, Inc., molecular weight 8,000)
B-3: Polytetrafluoroethylene-based wax (Lubron (Registered
Trademark) L5, available from Daikin Industries, Ltd.)
B-4: Pentaerythritol tetrastearate (WE-476, available from NOF
CORPORATION)
B-5: Calcium stearate (calcium stearate, available from NOF
CORPORATION)
<C: Antioxidant>
C-1:
Ethylenebis(oxyethylene)bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propio-
nate (IRGANOX (Registered Trademark) 245, available from BASF)
C-2:
Pentaerythritoltetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propion-
ate] (IRGANOX (Registered Trademark) 1010, available from BASF)
C-3:
1,3,5-Trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene
(THANOX (Registered Trademark) 330, available from Rianlon)
C-4:
N,N'-hexan-1,6-diylbis[3-(3,5-di-tert-butyl-4-hydroxyphenylpropionam-
ide] (IRGANOX (Registered Trademark) 1098, available from BASF)
Respective physical properties of the polyacetal resin composition
in Examples and Comparative examples were measured as follows. The
evaluation results of the polyacetal resin composition in Examples
and Comparative examples are shown in Table 1 to Table 3.
<Evaluation of Mold Releasability>
Evaluation of mold releasability was carried out as follows. A
container (box-shaped molded container) molded into a box shape of
30.times.50.times.30 mm having a rib at the center was continuously
and fully automatically molded using an injection molding machine
PS40 manufactured by Nissei Plastic Industrial Co., Ltd., and a
pressing pressure applied to the ejector pin when the box-shaped
molded container was released was measured using a pin type
pressure sensor. An average value of the pressing pressure applied
to the ejector pin from the eleventh shot to the thirtieth shot
among the 30-shot consecutive moldings was made the mold releasing
resistance value of each sample of Examples and Comparative
examples.
<Evaluation of Fuel Oil Resistance>
Evaluation of fuel oil resistance was carried out by the following
procedure. A schematic drawing of an apparatus used for evaluation
of fuel oil resistance was shown in the FIGURE. First, 300 ml of a
mixed solution of toluene/isooctane/methanol=42.5/42.5/15.0 vol %
was charged in a pressure-resistant sealed container as fuel for
evaluation of fuel oil resistance. About 10 g of glass wool was
charged in the pressure-resistant sealed container to which the
fuel had been charged, and the box-shaped molded container used for
the above-mentioned evaluation of releasability was placed on the
glass wool so as not to come into direct contact with the fuel.
Into the box-shaped molded container was charged 6 ml of the same
fuel, and the lid of the pressure-resistant sealed container was
closed.
The pressure-resistant sealed container into which the box-shaped
molded container had been charged was heated in a hot water bath at
60.degree. C. for 300 hours to expose the box-shaped molded
container to the vapor of the fuel. After the lapse of 300 hours,
the box-shaped molded container was taken out from the
pressure-resistant sealed container, the fuel attached to the
box-shaped molded container was air-dried, and then the inner
bottom surface of the box-shaped molded container was observed.
<Evaluation of Retention Thermal Stability>
The polyacetal resin compositions of Examples and Comparative
examples were each melted and maintained in a cylinder of IS75E-2B
manufactured by Toshiba Machine Co., Ltd., heated to 240.degree.
C., at intervals of 12 minutes up to 72 minutes at the maximum, and
then, a thin plate with a thickness of 3 mm was formed by molding
using the polyacetal resin composition, and the time (minute)
during which silver streak was observed in the molded thin plate
(molded piece) was evaluated by naked eyes. It is practical if the
time for observing silver streak is 48 minutes or longer, which
means that the longer shows excellent thermal stability.
<Evaluation Standard>
Evaluation standards for evaluation of mold releasability,
evaluation of fuel oil resistance and retention thermal stability
in Examples and Comparative examples are as follows.
Evaluation of Mold Releasability:
When the average value of pressing pressure applied to the ejector
pin (releasing resistance value) is 3.1 MPa or less, it is judged
as .circleincircle. (excellent), when it exceeds 3.1 MPa and 4.1
MPa or less, it is judged as .largecircle. (good), and when it
exceeds 4.1 MPa, it is judged as .times. (poor).
Evaluation of Fuel Oil Resistance:
It was evaluated by a ratio (elution amount) at which the eluted
component occupies the inner bottom surface portion of the
box-shaped molded container, and evaluated with the numerical
values of the following 1 to 5 stages. 1 is the best and 5 is the
worst.
1: Almost no elution is observed. 0%.ltoreq.Elution
amount.ltoreq.5%.
2: Very slight elution is observed. 5%.ltoreq.Elution
amount.ltoreq.10%.
3: Slight elution is observed. 10%.ltoreq.Elution
amount.ltoreq.25%.
4: Elution is observed. 25%.ltoreq.Elution amount.ltoreq.50%.
5: A large amount of elution is observed. 50%<Elution
amount.
TABLE-US-00001 TABLE 1 Example 1 Example 2 Example 3 Example 4
Formulation Polyacetal resin (A) 100 100 100 100 amount Mold
release agent (B-1) Hi-WAX 220MP (PE wax) 0.15 0.10 (parts by Mold
release agent (B-2) Hi-WAX 800P (PE wax) 0.15 mass) Mold release
agent (B-3) Lubron L5 (Teflon wax) 0.15 Mold release agent (B-4)
Pentaerythritol tetrastearate (PETS) Mold release agent (B-5)
Calcium stearate (StCa) Antioxidant (C-1) IRGANOX 245 0.30 0.30
0.30 0.30 Antioxidant (C-2) IRGANOX 1010 Antioxidant (C-3) THANOX
330 Antioxidant (C-4) IRGANOX 1098 Evaluation of Evaluation result
of mold releasability .largecircle. .largecircle. .largecircle.
.largecircle. physical Evaluation result of fuel oil resistance 3 3
2 3 property Retention thermal stability (unit: min) 72 60 60 72
Example 5 Example 6 Example 7 Example 8 Formulation Polyacetal
resin (A) 100 100 100 100 amount Mold release agent (B-1) Hi-WAX
220MP (PE wax) 0.05 0.10 0.10 0.05 (parts by Mold release agent
(B-2) Hi-WAX 800P (PE wax) mass) Mold release agent (B-3) Lubron L5
(Teflon wax) Mold release agent (B-4) Pentaerythritol tetrastearate
(PETS) Mold release agent (B-5) Calcium stearate (StCa) Antioxidant
(C-1) IRGANOX 245 0.30 0.20 0.05 0.05 Antioxidant (C-2) IRGANOX
1010 Antioxidant (C-3) THANOX 330 Antioxidant (C-4) IRGANOX 1098
Evaluation of Evaluation result of mold releasability .largecircle.
.largecircle. .circleincircle. .largecircle. physical Evaluation
result of fuel oil resistance 3 3 2 2 property Retention thermal
stability (unit: min) 72 72 48 48
TABLE-US-00002 TABLE 2 Example 9 Example 10 Example 11 Example 12
Formulation Polyacetal resin (A) 100 100 100 100 amount Mold
release agent (B-1) Hi-WAX 220MP (PE wax) 0.10 0.10 0.05 0.10
(parts by Mold release agent (B-2) Hi-WAX 800P (PE wax) mass) Mold
release agent (B-3) Lubron L5 (Teflon wax) Mold release agent (B-4)
Pentaerythritol tetrastearate (PETS) Mold release agent (B-5)
Calcium stearate (StCa) Antioxidant (C-1) IRGANOX 245 Antioxidant
(C-2) IRGANOX 1010 0.30 0.20 0.20 0.10 Antioxidant (C-3) THANOX 330
Antioxidant (C-4) IRGANOX 1098 Evaluation of Evaluation result of
mold releasability .largecircle. .largecircle. .largecircle.
.circleincircle. physical Evaluation result of fuel oil resistance
2 1 1 1 property Retention thermal stability (unit: min) 72 72 72
60 Example 13 Example 14 Example 15 Example 16 Formulation
Polyacetal resin (A) 100 100 100 100 amount Mold release agent
(B-1) Hi-WAX 220MP (PE wax) 0.10 0.15 0.10 0.10 (parts by Mold
release agent (B-2) Hi-WAX 800P (PE wax) mass) Mold release agent
(B-3) Lubron L5 (Teflon wax) Mold release agent (B-4)
Pentaerythritol tetrastearate (PETS) Mold release agent (B-5)
Calcium stearate (StCa) Antioxidant (C-1) IRGANOX 245 Antioxidant
(C-2) IRGANOX 1010 0.05 Antioxidant (C-3) THANOX 330 0.10 0.05
Antioxidant (C-4) IRGANOX 1098 0.05 Evaluation of Evaluation result
of mold releasability .circleincircle. .largecircle.
.circleincircle. .circleinci- rcle. physical Evaluation result of
fuel oil resistance 1 1 1 2 property Retention thermal stability
(unit: min) 60 72 72 48
TABLE-US-00003 TABLE 3 Comparative Comparative Comparative
Comparative example 1 example 2 example 3 example 4 Formulation
Polyacetal resin (A) 100 100 100 100 amount Mold release agent
(B-1) Hi-WAX 220MP (PE wax) 2.0 (parts by Mold release agent (B-2)
Hi-WAX 800P (PE wax) mass) Mold release agent (B-3) Lubron L5
(Teflon wax) Mold release agent (B-4) Pentaerythritol tetrastearate
(PETS) 0.15 Mold release agent (B-5) Calcium stearate (StCa) 0.15
Antioxidant (C-1) IRGANOX 245 0.30 0.30 0.30 0.30 Antioxidant (C-2)
IRGANOX 1010 Antioxidant (C-3) THANOX 330 Antioxidant (C-4) IRGANOX
1098 Evaluation of Evaluation result of mold releasability X
.largecircle. .largecircle. .circleincircle. physical Evaluation
result of fuel oil resistance 1 5 5 5 property Retention thermal
stability (unit: min) 72 36 12 48
From Examples 1 to 16 and Comparative examples 1 to 4, it can be
understood that the polyacetal resin compositions comprising (A)
the polyacetal resin and the polyolefin-based wax and/or the
polytetrafluoroethylene-based wax as (B) the mold release agent,
and the content of (B) the mold release agent in the polyacetal
resin composition being 0.01 part by mass or more and 1.0 part by
mass or less based on 100 parts by mass of (A) the polyacetal resin
are excellent in mold releasability, fuel oil resistance and
thermal stability. Comparative example 1 which is an example of a
polyacetal resin composition to which no (B) mold release agent is
added, showed good fuel oil resistance and thermal stability, but
mold releasability was not good since no (B) mold release agent was
added. On the other hand, it can be understood that the polyacetal
resin compositions of Comparative example 2 in which
pentaerythritol tetrastearate which is a fatty acid ester is used
as the mold release agent, and Comparative example 3 in which
calcium stearate which is a fatty acid metal salt is used as the
mold release agent showed good mold releasability but fuel oil
resistance and thermal stability are not good. In addition, it can
be understood that Comparative example 4 which is an example in
which (B) the mold release agent is used with an excessive amount,
is excellent in mold releasability but fuel oil resistance is not
good even when (C) the antioxidant is used in combination.
Examples 9 to 15 are examples in which
pentaerythritol-tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]
and/or
1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benze-
ne is/are used as (C) the antioxidant, and it can be understood
that these are more excellent in mold releasability, fuel oil
resistance and thermal stability.
Examples 12, 13 and 15 are examples in which the content of (B) the
mold release agent in the polyacetal resin composition is 0.08 part
by mass or more and 0.12 part by mass or less based on 100 parts by
mass of (A) the polyacetal resin, and the content of (C) the
antioxidant is 0.03 part by mass or more and 0.15 part by mass or
less based on 100 parts by mass of (A) the polyacetal resin, and it
can be understood that these are particularly excellent in
releasability, fuel oil resistance and thermal stability.
From the above, it can be understood that the polyacetal resin
composition comprising (A) a polyacetal resin and (B) a mold
release agent, (B) the mold release agent is a polyolefin-based wax
and/or a polytetrafluoroethylene-based wax, and the content of (B)
the mold release agent in the polyacetal resin composition is 0.01
part by mass or more and 1.0 part by mass or less based on 100
parts by mass of (A) the polyacetal resin is excellent in thermal
stability, little elution of components of the resin composition
upon brought into contact with fuel, and good releasability from a
mold at the time of molding, and is excellent in the points of
thermal stability, fuel oil resistance and mold releasability.
* * * * *